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Cisco ME 3400 EthernetAccess Switch SoftwareConfiguration Guide
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Chapter32 Configuring IP Unicast Routing Configuring BGP
Configuring Route Dampening
Route flap dampening is a BGP feature designed to minimize t he propagation of flapping routes across
an internetwork. A route is considered to be flapping when it is repeatedly available, then unavailable,
then available, then unavailable, and so on. When route dampening is enabled, a numeric penalty value
is assigned to a route when it flaps. When a route’s accumulated penalties reach a configurable limit,
BGP suppresses advertisements of the route, even if the route is running. The reuse limit is a
configurable value that is compared with the penalty. If the penalty is less than the reuse limit, a
suppressed route that is up is advertised again.
Dampening is not applied to routes that are learned by IBGP. This policy prevents the IBGP peers from
having a higher penalty for routes external to the AS.
Beginning in privileged EXEC mode, use these commands to configure BGP route da mp enin g:
To disable flap dampening, use the no bgp dampening router configuration command without
keywords. To set dampening factors back to the default values, use the no bgp dampening router
configuration command with values.
Step6 end Return to privileged EXEC mode.
Step7 show ip bgp Verify the configuration. Display the originator ID and the
cluster-list attributes.
Step8 copy running-config startup-config (Optional) Save your entries in the configuration file.
Command Purpose
Command Purpose
Step1 configure terminal Enter global configuration mode.
Step2 router bgp autonomous-system Enter BGP router configuration mode.
Step3 bgp dampening Enable BGP route dampening.
Step4 bgp dampening half-life reuse suppress
max-suppress [route-map map](Optional) Change the default values of route dampe ning
factors.
Step5 end Return to privileged EXEC mode.
Step6 show ip bgp flap-statistics [{regexp regexp} |
{filter-list list} | {address mask [longer-prefix]}] (Optional) Monitor the flaps of all paths that are flapping. The
statistics are deleted when the route is not suppressed and is
stable.
Step7 show ip bgp dampened-paths (Optional) Display the dampened routes, including the time
remaining before they are suppressed.
Step8 clear ip bgp flap-statistics [{regexp regexp} |
{filter-list list} | {address mask [longer-prefix]} (Optional) Clear BGP flap statistics to make it less likely that a
route will be dampened.
Step9 clear ip bgp dampening (Optional) Clear route dampening information, and unsuppress
the suppressed routes.
Step10 copy running-config startup-config (Optional) Save your entries in the configuration file.